[#800] Replace fmt with prettyprinter

Description

• Add Fmt to morley-prelude

  I thought about splitting it into its own library, but that seems like more trouble than it's worth.

  This Fmt is implemented on top of Prettyprinter and is essentially an API compatibility layer. But it differs from prettyprinter in some important ways, primarily in how it handles newlines.

• Remove and/or deprecate things obsoleted by the change

• Remove redundant RenderDoc instances.

  There are quite a few RenderDoc instances whose only purpose is to be used in instance Buildable X where build = buildRenderDoc. Since Buildable now also produces Doc, it makes a lot of sense to write Buildable directly and drop the middleware.

• Chore: Turns out, Prettier doesn't do anything since 3743d6ae, so deprecate it.

Related issue(s)

Resolves #800 (closed)

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